A general loss of muscle mass or atrophy is a characteristic response to fasting, as well as many diseases, including advanced cancer, renal failure, sepsis, cachexia, arthritis, osteoporosis, and diabetes. Atrophy of muscles also results from their disuse or denervation, e.g., immobilization, muscle unloading, spinal cord injury etc., and atrophy contributes substantially to many common health problems, including but not limited to HIV, chronic heart failure, chronic kidney disease, liver cirrhosis, burn injuries, osteoporosis, arthritis etc. Regardless of the cause of muscle atrophy, skeletal muscle atrophy is characterized by a decrease in protein content, fiber diameter, force production, and fatigue resistance.
Loss of muscle mass associated with progression of atrophy has been studied in animals subjected to denervation, immobilization, starvation, and animals implanted with cancer cells capable of inducing muscle wasting. Alternatively, atrophy can be induced in animals subjected to glucocorticoid administration. In these animals, the degree of muscle wasting can be assessed by employing a variety of measurements that record changes in muscle weights or fiber cross sectional area, and by performing kinetic experiments using a large number of animals etc. Detecting a significant change in muscle mass or in kinetics often requires a long waiting period. Measurement of muscle weight and fiber cross sectional area require cumbersome surgical procedures, cross-sectional area measurements and often the animal is sacrificed. Thus, such procedures usually require a large number of animals and precludes being able to follow a set of muscles, temporally, in the same animal.
Certain aspects of this disclosure relate to a method for inducing an atrophy response.